Airline passengers pass through security on May 2, at Orlando International Airport in Orlando, Florida. Security in airports and train stations has been increased in the wake of the death of Osama bin Laden.

Documents found in the US raid on Osama bin Laden's compound indicate that Al Qaeda was plotting an attack on the US rail system, possibly for the 10th anniversary of the 9/11 attacks. The information, the first major disclosure from what may be the largest intelligence haul since 9/11, comes as Al Qaeda confirmed its leader's death in a statement on jihadist websites, saying that bin Laden's blood "would not be wasted."

The discovery of the documents in Mr. bin Laden's hideout show that he was actively involved in planning attacks, debunking the commonly held belief that he had been reduced to merely a figurehead of Al Qaeda while in hiding. "He continued to plot and plan, to come up with ideas about targets and to communicate those ideas to other senior Qaeda leaders," an unnamed US official briefed on the documents told The New York Times.

"It's the first time we've gotten something directly from him," a US counterterrorism official told the Journal. "There was nothing new in it. What's different about it is it was in bin Laden's house."

Intelligence officials have made translating and analyzing the information found in the compound a top priority so that any plots already in the works can be disrupted.

Following the US raid on bin Laden's compound early May 2, American transportation facilities were put on heightened alert in anticipation of possible revenge attacks by Al Qaeda, with increased security at airports in particular.

Mass transport such as trains and subways are more difficult to secure. To date, random checks with bomb-sniffing dogs have been the most common security measure, rather than checkpoints to screen every passenger, as is done in airports.

The March 2004 bombings of commuter trains in Madrid resulted in 191 deaths and about 1,800 people injured, the L.A. Times reports. In July 2005, 52 people died and about 700 were injured when suicide bombers attacked three subway trains and a double-decker bus in London.

No new alert has been issued because the note discussing the attack lacked specifics, according to the DHS statement:

We want to stress that this alleged Al Qa’ida plotting is based on initial reporting, which is often misleading or inaccurate and subject to change. We remain at a heightened state of vigilance, but do not intend to issue an NTAS alert at this time. We will issue alerts only when we have specific or credible information to convey to the American public.

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